The central themes of this program project are the mechanism and regulation of lipoprotein metabolism and the role that apoproteins play in lipid and lipoprotein homeostasis. Studies of reverse cholesterol transport and interstitial fluid lipoprotein metabolism will be emphasized. Our program project uses a multidisciplinary approach involving biochemistry, cell biology, physiology, immunochemistry and electron microscopy. We are approaching these problems by utilizing models at the subcellular, cellular, isolated organ level and in whole animal models, including humans. We plan to study biogenesis of lipoproteins by de novo synthesis and remodeling of lipoproteins within hepatic or intestinal organelles. Studies of extracellular lipoprotein remodeling in the interstitium and its possible role in reverse cholesterol transport will be continued. Recent studies have indicated that the pre-beta A-I particles may play a pivotal role in reverse cholesterol transport. We are planning to elucidate the origin, formation and function of the pre-beta particles and evaluate their role in the pathophysiology of lipoprotein metabolism using the expertise and techniques available in all projects. Our studies on prenodal peripheral lymph in dogs will be extended to studies of human interstitial fluid lipoprotein metabolism. Our method for collecting human interstitial fluid does not involve alterations of capillary permeability. We are planning to characterize human interstitial fluid lipoprotein composition in normal individuals and in different pathological conditions and assess the effects of dietary or drug interventions. All of our projects require the development of micromethodologies to allow analysis of very small samples. We are continuing and extending the development of advanced methodologies for lipoprotein analysis. We believe that these studies will contribute to our understanding of lipoprotein-apolipoprotein metabolism and its physiological role in lipid homeostasis.